As techniques for color hard copy, a heat-sensitive transfer method, an electrophotographic method, an ink jet recording method, etc., have been vigorously investigated. A heat-sensitive transfer method is advantageous in various ways as compared to other systems because the maintenance and operation of the apparatus are easy and the apparatus and expendable supplies are inexpensive.
Examples of heat-sensitive transfer system include a system of heating a heat-sensitive transfer material having a heat-fusible ink layer on a base film by a thermal head to fuse the ink and transferring the ink onto an ink-receiving sheet as records, and a system of heating a heat-sensitive transfer material having a coloring material layer containing a sublimable dye on a base film by a thermal head to sublime the dye and transfer the dye onto a dye-receiving sheet. Between these systems, the latter sublimation transfer system is particularly advantageous for full color recording of high image quality since in the system, by changing the energy being applied to a thermal heat, the transferring amount of dyes can be changed, which allows for gradation recording.
However, there are various restrictions on sublimable dyes used in the system and there are few dyes which possess all the required properties.
The dye for the sublimation transfer system is required for have, for example, such properties that the dye has preferred spectral characteristics for color reproduction, is sublimable, a high fastness to light and heat, a high strength to various chemicals, can be easily synthesized, and which allows for a heat-sensitive transfer material containing the dye(s) to be easily prepared. Due to the recent requirement of the increase of image quality, the development of sublimable dyes having excellent spectral characteristics has been desired.
In general, a full color is formed by the combination of three colors of yellow, magenta, and cyan dyes. Among them, a magenta dye is in a position between yellow and cyan and hence the requirement for spectral characteristics on the magenta dye is most critical. Thus, the development of sublimable magenta dyes having excellent spectral characteristics has been desired.
Various kinds of magenta dyes for heat-transfer recording have been proposed. For example, there are anthraquinone series magenta dyes disclosed in JP-A-60-131293, 60-159091, 61-227093, 61-262190, etc., (the term "JP-A" as used herein means an "unexamined published Japanese patent application) and azo series magenta dyes disclosed in JP-A-60-30391, 60-30392, 60-30394, 61-227091, 61-227092, etc.
However, the spectral characteristics of these magenta dyes are far from ideal and the absorption range thereof is broad and has a considerably large side absorption.